The Chromium browser window is represented by several objects, some of which are included in this diagram:
The frame is the portion of the browser window that includes the title bar, sizing borders, and other areas traditionally known as the "non-client" areas in Windows terminology. We supply a frame (called BrowserFrame) that subclasses the views::Widget class that adds some additional handling on Vista for DWM adjustments behind the TabStrip, etc. On Windows Vista, we only use the glass mode when desktop compositing is enabled; in Classic or Vista Basic modes we use the XP Luna mode. Because the user is able to toggle the compositing on and off by changing Windows themes, we need to be able to dynamically change frame mode. For more information about how this is done in views, see the views::Widget documentation. The browser window provides two NonClientFrameView subclasses - GlassBrowserFrameView and OpaqueBrowserFrameView which are swapped in the BrowserFrame's NonClientView when DWM is toggled.
The BrowserView object contains all of the elements that are common between the frames that are part of the presentation of the browser window - the tab strip, the toolbar, the bookmarks bar, and other elements of the UI. When the frame changes, this View is inserted into the new NonClientView.
The BrowserView implements an interface called BrowserWindow, which the Browser object uses to interact with the View.
This is the core state and command execution component of a Browser window. It interacts with an abstract Browser Window interface to update the UI. This allows us to write unit tests that supply a windowless "testing view" and then execute high-level functionality within the browser from within the unit testing framework, rather than running UI tests.